Someone on my FM thread recently discovered that the VF confirmation range increases dramatically when AF is set to MF (on either body or lens) vs leaving AF enabled and using back-button focusing as a way to avoid triggering a lens refocus when checking for VF focus confirmation. I always use back-button focusing when I DotTune but I told everyone in my video to disable AF because I thought is would be an easier procedure for those who aren't already familiar with back-button focusing. I failed to test that step before describing it to others, sorry!

When I toggle AF/MF I see an immediate change to the confirmed range. Here are the results of a DotTune with AF enabled vs AF disabled:

AF enabled: -14 to -18

AF disabled: -2 to -20 (past end of -20 range)

My theory is that Nikon's firmware is intentionally expanding the in-focus range for VF confirmation (when AF is disabled) to make it easier and faster for photographers to manually focus. They probably figured that if the range were tight it would be too difficult and time consuming for people to manually focus to it.

So here is an important update to the DotTune method described in the video:

Configure your body for back-button focusing by setting "AF activation" to "AF-ON only". On this D800 this is option a4

After establishing critical focus of your AF target, leave the body and lens to set AF rather than switching to MF

During the DotTune VF range-discovery procedure (step 4 and 5 in my video), use a half-press of the shutter to turn on the VF confirmation. In my video I said you could use either a half-press of the shutter *or* the AF-ON button, but now that we're leaving AF enabled you must use a half-press of the shutter.

Note that when the body+lens are set to AF the VF confirmation display wont stay illuminated for the duration of the metering timeout like it does when the body or lens are set to MF. This means you have to hold the shutter half-pressed to keep the confirmation display active while checking for the dot.